Alterations in cellular and humoral immunity have been described in both uveitis and ocular tumors; however the biologic importance of these alterations are unclear. Is the reactivity towards ocular antigens important in the pathophysiology of these diseases or is it an epiphenomenon secondary to non-immunologic alterations of tissue antigens? Circulating immune complexes (consisting of antigen-antibody) have been demonstrated in both animal models and human diseases. These complexes can adversely affect the host by mediating tissue destruction in a number of ways. There is preliminary evidence that both uveitis and ocular tumor patients have elevated levels of immune complexes. We have done preliminary work using extremely sensitive assays to measure immune complexes in these patients and have observed elevated levels in both the Raji cell radioimmunoassay and the C1q radiolabeled binding assay. It is possible that the antigens which resulted in the development of these immune complexes are important in the pathophysiology of these diseases. A meticulous study of immune complexes in ocular disease may provide basic information regarding the etiology of both uveitis as well as a greater understanding of the host's defense mechanism in ocular malignancy. Separation, characterization, and ultrastructual location of the antigens from immune complexes will allow us to determine their origin and nature. It is possible that studies of immune complexes, their separated components, and the host's immunologic response to them in these diseases may enable us to elucidate the events which are important in the pathogenesis of these diseases. In addition to increasing our basic understanding of these diseases it is possible that by using these separated and purified antigenic components we may be able to develop more sensitive and specific assays for use clinically in the immunodiagnosis, monitoring, and possibly therapy of these patients with ocular tumors or uveitis.